This invention generally relates to printing apparatus and methods and more particularly relates to a printing apparatus and method including an electromagnetic interference reducing optical data link for transmitting image forming data.
In the typical printer, a carriage carrying a print head translates linearly along one dimension of a receiver as the receiver is held momentarily stationary beneath the print head, whereupon the print head prints one or more lines of image data on the receiver. After one sweep of the carriage, the receiver is advanced a predetermined distance and another sweep is performed to print another line of image data on the receiver. By modulating the image data in synchronization with translation speed of the receiver, a complete raster image is eventually printed or exposed onto the receiver.
In such printers, an image control computer conventionally communicates with the print head by means of a flexible electrical cable with multiple conductor wires therein. The wires in the cable carry the image forming data from the computer to the print head. However, it is known that electromagnetic radiation and power supply noise are generated by the printer""s components, such as electrical cabling, switched mode power supplies, direct current and alternating current converters, external monitor input and output devices, power ports, clock generators, electronic circuitry and computers. The electromagnetic radiation emitting from the cable in addition to the computer and any electronic circuitry present therein may interfere with proper operation of nearby electronic devices.
As stated hereinabove, the flexible cable interconnects the control computer to the print head in order to transmit image forming data between the computer and the print head. This results in a radio frequency electromagnetic field emitting from the flexible cable. As image resolutions and data bit depths increase, the frequency of data and clock signals that are transmitted along the cable also increase. In addition, as image widths increase, length of the flexible cable, and therefore electromagnetic radiation emissions, also increase. Moreover, as control computer clock frequencies increase, it becomes more difficult to limit these electromagnetic emissions to international regulatory standards, such as standards promulgated by the United States Government Federal Communications Commission (FCC), as well as national governments worldwide. Prior art solutions to the problems recited hereinabove have been to increase the number of conductors in the cable, to increase the cable shielding or even completely shield the printer. However, these solutions increase size, weight and cost of the printer.
A typical non-contact LED (Light Emitting Diode) array image printer is disclosed in U.S. Pat. No. 4,837,589 titled xe2x80x9cNon-Contact LED-Array Image Printerxe2x80x9d issued Jun. 6, 1989 in the name of Dennis W. Dodge. This patent discloses that an LED array is mounted on a substrate bearing an interface control circuit which receives video data through a ribbon cable. The LED array is imaged by a lens onto an exposure plane on a platen parallel to the direction of scanning. A photosensitive medium is driven in registration in forward and reverse directions biased against the exposure platen which defines the image plane. However, the device disclosed by this patent still uses a ribbon cable to transmit video data to the control circuit. Thus, this patent does not disclose a suitable solution to the problem of electromagnetic radiation caused by transmission of the video data to the control circuit.
Therefore, there has been a long-felt need to provide an apparatus and method including an electromagnetic interference reduction technique for transmitting image forming data.
The invention resides in a printer apparatus having an electromagnetic interference reducing optical data link transmitting image forming data. The printer comprises a print head capable of being actuated to form the image on a receiver. More specifically, a photodetector is connected to the print head for detecting image forming data carried by an infrared light beam. The photodetector also actuates the print head in response to the image forming data detected by the photodetector in order to print the image on the receiver. In addition, also provided is a light source in optical communication with the photodetector for emitting the light beam to be received by the photodetector. In this manner, the photodetector detects the image forming data as the light source emits the light beam and the print head is actuated with this image forming data. The print head forms the image on the receiver in accordance with the image forming data. In this manner, image forming data is transmitted from the light source to the print head by means of the light beam, thereby removing high frequency electronic signals from any interconnecting flexible multiconductor electrical cable which would otherwise emit undesirable high frequency electromagnetic radiation harmful to operation of any nearby electronic devices.
The printer apparatus also comprises a controller, which may be a computer, connected to a carriage carrying the print head for supplying control data to the carriage in order to control movement of the carriage. Such a controller emits a first electromagnetic field. In order to ameliorate the first electromagnetic field, a first shielding enclosure surrounds the controller and thereby shields against the first electromagnetic field. A carriage is connected to the print head for carrying the print head relative to the receiver. The carriage includes electronic circuitry therein for electrically actuating the print head in response to the image forming data detected by the photodetector. Such electronic circuitry emits a second electromagnetic field. In order to ameliorate the second electromagnetic field, a second shielding enclosure surrounds the carriage and associated electronic circuitry and thereby shields against the second electromagnetic field. The previously mentioned flexible multiconductor electronic cable is provided to transfer low frequency electronic signals between the controller and the carriage. Since only low frequency electronic signals are transmitted via this cable, it is easier to reduce electromagnetic emissions to comply with the aforementioned Governmental limits. Thus, other electronic devices which may be in the vicinity of the printer are shielded from electromagnetic radiation emitting from the controller and electronic circuitry in the carriage.
A support member, which may be a platen, is disposed near the print head for supporting the receiver at a position adjacent the print head. A translation member, which may be a roller, is disposed adjacent the support member, the translation member being capable of intimately engaging the receiver for translating the receiver through a nip defined between the print head and the support member. Also provided is a first motor engaging the roller for rotating the roller, so that the receiver translates through the nip as the first motor rotates the roller. In addition, a rotatable lead screw threadably engages the carriage for translating the carriage along the lead screw. A second motor rotates the lead screw, so that the carriage translates along the lead screw as the lead screw rotates.
An object of the present invention is to provide a printing apparatus and method including an electromagnetic interference reducing optical data link for transmitting image forming data to a print head included in the printing apparatus.
A feature of the present invention is the provision of a light source emitting an infrared light beam carrying high frequency image forming data detectable by a photodetector connected to the print head but spaced-apart from the light source, which photodetector converts the image forming data into electrical pulses by means of electrical circuitry which in turn controls printing on the receiver by the print head that is connected to the photodetector.
These and other objects, features and advantages of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawings wherein there is shown and described illustrative embodiments of the invention.